1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
|
/*
* Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License").
* You may not use this file except in compliance with the License.
* A copy of the License is located at
*
* http://aws.amazon.com/apache2.0
*
* or in the "license" file accompanying this file. This file is distributed
* on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
* express or implied. See the License for the specific language governing
* permissions and limitations under the License.
*/
#include <stdbool.h>
#include "error/s2n_errno.h"
#include "utils/s2n_blob.h"
#include "tls/s2n_cipher_suites.h"
#include "tls/s2n_server_extensions.h"
#include "tls/s2n_tls.h"
#include "tls/s2n_tls13.h"
#include "tls/s2n_tls13_handshake.h"
#include "utils/s2n_safety.h"
#include "pq-crypto/s2n_pq.h"
/* From RFC5246 7.4.1.2. */
#define S2N_TLS_COMPRESSION_METHOD_NULL 0
/* from RFC: https://tools.ietf.org/html/rfc8446#section-4.1.3*/
uint8_t hello_retry_req_random[S2N_TLS_RANDOM_DATA_LEN] = {
0xCF, 0x21, 0xAD, 0x74, 0xE5, 0x9A, 0x61, 0x11, 0xBE, 0x1D, 0x8C, 0x02, 0x1E, 0x65, 0xB8, 0x91,
0xC2, 0xA2, 0x11, 0x16, 0x7A, 0xBB, 0x8C, 0x5E, 0x07, 0x9E, 0x09, 0xE2, 0xC8, 0xA8, 0x33, 0x9C
};
int s2n_server_hello_retry_send(struct s2n_connection *conn)
{
POSIX_ENSURE_REF(conn);
POSIX_CHECKED_MEMCPY(conn->handshake_params.server_random, hello_retry_req_random, S2N_TLS_RANDOM_DATA_LEN);
POSIX_GUARD(s2n_server_hello_write_message(conn));
/* Write the extensions */
POSIX_GUARD(s2n_server_extensions_send(conn, &conn->handshake.io));
/* Update transcript */
POSIX_GUARD(s2n_server_hello_retry_recreate_transcript(conn));
/* Reset handshake values */
conn->handshake.client_hello_received = 0;
conn->client_hello.parsed = 0;
POSIX_CHECKED_MEMSET((uint8_t*) conn->extension_requests_received, 0, sizeof(s2n_extension_bitfield));
return 0;
}
int s2n_server_hello_retry_recv(struct s2n_connection *conn)
{
POSIX_ENSURE_REF(conn);
POSIX_ENSURE(conn->actual_protocol_version >= S2N_TLS13, S2N_ERR_INVALID_HELLO_RETRY);
const struct s2n_ecc_preferences *ecc_pref = NULL;
POSIX_GUARD(s2n_connection_get_ecc_preferences(conn, &ecc_pref));
POSIX_ENSURE_REF(ecc_pref);
const struct s2n_kem_preferences *kem_pref = NULL;
POSIX_GUARD(s2n_connection_get_kem_preferences(conn, &kem_pref));
POSIX_ENSURE_REF(kem_pref);
const struct s2n_ecc_named_curve *named_curve = conn->kex_params.server_ecc_evp_params.negotiated_curve;
const struct s2n_kem_group *kem_group = conn->kex_params.server_kem_group_params.kem_group;
/* Boolean XOR check: exactly one of {named_curve, kem_group} should be non-null. */
POSIX_ENSURE( (named_curve != NULL) != (kem_group != NULL), S2N_ERR_INVALID_HELLO_RETRY);
/**
*= https://tools.ietf.org/rfc/rfc8446#4.2.8
*# Upon receipt of this extension in a HelloRetryRequest, the client
*# MUST verify that (1) the selected_group field corresponds to a group
*# which was provided in the "supported_groups" extension in the
*# original ClientHello
**/
bool selected_group_in_supported_groups = false;
if (named_curve != NULL && s2n_ecc_preferences_includes_curve(ecc_pref, named_curve->iana_id)) {
selected_group_in_supported_groups = true;
}
if (kem_group != NULL && s2n_kem_preferences_includes_tls13_kem_group(kem_pref, kem_group->iana_id)) {
selected_group_in_supported_groups = true;
}
/**
*= https://tools.ietf.org/rfc/rfc8446#4.2.8
*# and (2) the selected_group field does not
*# correspond to a group which was provided in the "key_share" extension
*# in the original ClientHello.
**/
bool new_key_share_requested = false;
if (named_curve != NULL) {
new_key_share_requested = (named_curve != conn->kex_params.client_ecc_evp_params.negotiated_curve);
}
if (kem_group != NULL) {
/* If PQ is disabled, the client should not have sent any PQ IDs
* in the supported_groups list of the initial ClientHello */
POSIX_ENSURE(s2n_pq_is_enabled(), S2N_ERR_PQ_DISABLED);
new_key_share_requested = (kem_group != conn->kex_params.client_kem_group_params.kem_group);
}
/**
*= https://tools.ietf.org/rfc/rfc8446#4.2.8
*# If either of these checks fails, then
*# the client MUST abort the handshake with an "illegal_parameter"
*# alert.
*
*= https://tools.ietf.org/rfc/rfc8446#section-4.1.4
*# Clients MUST abort the handshake with an
*# "illegal_parameter" alert if the HelloRetryRequest would not result
*# in any change in the ClientHello.
**/
POSIX_ENSURE(new_key_share_requested, S2N_ERR_INVALID_HELLO_RETRY);
POSIX_ENSURE(selected_group_in_supported_groups, S2N_ERR_INVALID_HELLO_RETRY);
/* Update transcript hash */
POSIX_GUARD(s2n_server_hello_retry_recreate_transcript(conn));
/* Reset handshake values */
POSIX_CHECKED_MEMSET((uint8_t*) conn->extension_requests_sent, 0, sizeof(s2n_extension_bitfield));
return S2N_SUCCESS;
}
|
